Air venting valve of vulcanising mould

ABSTRACT

An air venting valve and method for removing air from a vulcanizing mould of a vehicle tire by the aid of an air venting valve having a body functioning as an air channel and an inner part movable in a longitudinal direction. The body includes a stem and a valve disc disposed at an inner end of the stem on the side of a mould surface, the diameter of the valve disc is larger than the inner diameter of the body. A spring member is arranged in the air venting valve for forcing the inner part in a predetermined position for opening the valve when a blank is removed from the vulcanizing mould. The lower part of the inner part of the body includes an outer thread and in the lower part of the body a respective inner thread for screwing the valve stem in the body.

This application is a Divisional of co-pending application Ser. No.12/668,315 filed on Jan. 8, 2010 and for which priority is claimed under35 U.S.C. §120. Application Ser. No. 12/668,315 is the national phase ofPCT International Application No. PCT/FI2008/000086 filed on Jul. 9,2008 under 35 U.S.C. §371 which claims priority to Finland ApplicationNo. 20075535 filed Jul. 11, 2007. The entire contents of each of theabove-identified applications are hereby incorporated by reference.

FIELD OF ART

This invention relates to an air venting valve for removing air from avulcanising mould.

In the air venting valve, there is a body functioning as an air channeland an inner part moving in its longitudinal direction which comprises astem, an outer diameter of which is smaller than an inner diameter ofthe body, and a valve disc at the inner end of the stem on the side of amould surface, a diameter of which valve disc is larger than the innerdiameter of the body.

The valve disc supports itself in a closing position of the air ventingvalve on a stop surface in the body and is in an open position at aclearance from said stop surface.

Furthermore, a spring member has been arranged in the air venting valvefor forcing the inner part in a predetermined position, particularly foropening the valve when a blank is removed from the vulcanising mould.

The invention also relates to a method for removing air from avulcanising mould of a vehicle tyre by means of an air venting valve.

PRIOR ART

In the vulcanising moulds of vehicle tyres, air venting holes orchannels are used because, in the vulcanising of the tyre, a tyre blanksmaller than the inner dimensions of the mould is placed inside themould, after which the mould is closed and, after which closing, thetyre blank is caused to expand whereby it presses against the surface ofthe mould in its plastic mode acquiring the size and shape of a tyre. Inconnection with closing the vulcanising mould, air between the tyreblank and the mould surface has to be removed in order for the surfaceof the tyre blank to come into a tight contact with the mould surface.There should be several of these air removal holes or channels in orderfor air to be removed completely at each point of the mould and no airpockets to remain between the tyre and the mould.

Specifications EP0774333 and U.S. Pat. No. 4,347,212 describe an airventing valve to be used in air venting channels in vulcanising mouldsof vehicle tyres, in which there are a stem inside the air ventingchannel, thinner than the diameter of the channel, and a valve discwhich is fast in the stem and is located in the area of the mouldsurface. On the inner surface of the mould, there is a stop recess forthe valve disc. Around the stem is located a coil spring which supportsitself in the mould and the valve disc either directly or via the stemand a flange fastened in it. The spring tries to press the valve discaway from the mould wall towards the tyre blank, whereby air is able toexit the mould via a clearance between the valve disc and the stoprecess and further via a gap between the stem and the air ventingchannel. As the material being vulcanised, when expanding, advancestowards the mould surface, it pushes ahead of it the valve disc whichthen finally presses tightly in the stop recess closing the air channel,whereby the material being vulcanised cannot access the air ventingchannel. The spring then opens the valve as the tyre blank is removedfrom the mould.

A disadvantage of known air venting valves is particularly their complexstructure and awkward installability. The air venting valve according tospecification U.S. Pat. No. 4,347,212 has no actual body in the valveand the fastening takes place from the backside of the mould. At itsbottom, there is a nut by which the valve stem is locked in place. Thevalve cannot be replaced without detaching the whole valve from themould or replacing the valve is extremely difficult. In the arrangementaccording to specification EP0774333, again, the stem is somewhat longerthan the air venting channel and, due to the dismantling possibility ofthe valve sleeve, the stop has been implemented by a snap joint betweenthe valve stem and the valve body realised by a clearance or,respectively, by a snap joint between the valve and each segment of thevulcanising mould realised by a clearance. In these known arrangements,the valve cannot be replaced without detaching the whole valve from themould or replacing the valve is extremely difficult. In the arrangementaccording to specification EP0774333, replacing the valve is relativelyawkward.

SUMMARY OF INVENTION

The object of this invention is to eliminate the disadvantages of knownprior art and to provide a totally novel air venting valve to be used inthe vulcanising moulds of vehicle tyres.

In the arrangement according to the invention, the valve body isdetachable and the valve can be installed from the front, whereby therecan be projections in the valve in its body for turning it closed/open.

Also the inner part of the valve can be detachably arranged to the body.For this, there is a thread in the lower part of the valve stem. Thereis a respective thread in the lower part of the valve body (the lowerpart of the channel). Locking is provided by screwing the valve stempast the thread of the body i.e., in the installation stage, the valvedisc is screwed through the body, whereby it stays permanently fast.

This is possible because the inner part is substantially longer than thebody, and because there is a 0.2-0.6 mm functional aperture (clearance)in the valve. When the thread in the valve stem ends, it stays fastbecause the thread part is larger than the free hole when they are notwithin each other.

With the arrangement according to the invention, the followingadvantages are gained:

-   the arrangement is simultaneously both permanently fast and    detachable,-   precise opening is provided,-   installing is possible in the last stage of the process,-   replacing is possible without having to replace the whole valve.

The characteristic features of the arrangement according to theinvention will be described in detail in the independent claims andadvantageous embodiments in the dependent claims.

BRIEF DESCRIPTION OF DRAWINGS

In the following, the invention will be described in detail by means ofan example with reference to the accompanying drawings in which

FIGS. 1-3 show an air venting valve according to the invention and aninner part and a body of the air venting valve separately

FIGS. 4 and 5 show the operation of the air venting valve according tothe invention, and

FIGS. 6, 7 and 8 show the valve stem and the valve body individually andwhen in operative engagement.

DETAILED DESCRIPTION OF ADVANTAGEOUS EMBODIMENT OF INVENTION

The inner surface of the vulcanising mould of a vehicle tyre providesthe vulcanised tyre its outer surface shape and tread patterns withtheir details in the tread area. Thus, on the mould surface of thevulcanising mould which shapes the tread there are, inter alia, bulgesforming tread grooves and recesses forming pattern parts. In thevulcanising mould, there is a large set of air venting valves 1 in whichthere is a cylindrical body 2 smooth of its outer surface or providedwith outer threads, within which is formed an air venting channel, whichchannels are advantageously both in the area of the tread and in thearea of the tyre sides which is not shown in the figures. The airventing channels extend through the wall of the vulcanising mould frominside the mould outside the mould.

There are different numbers of the air venting valves 1 in thevulcanising moulds of vehicle tyres depending on the size and type ofthe tyre. For example, there are typically 700-900 and 2,000-2,400 airventing channels, respectively, in the summer and winter tyres ofpassenger cars.

In the air venting valve 1, there are, in the longitudinal direction ofthe body functioning as an air venting channel, a moving inner part 3which comprises a stem 4, an outer diameter D4 of which is smaller thanan inner diameter D2 of the body, and a valve disc 5 at an inner orupper end of the stem 4 on the side of a mould surface. A centre line ofthe stem 4 is straight and is located inside the body 2 which is alsostraight of its centre line and, furthermore, the lengthwise directionof the stem is the same as the longitudinal direction of the body,whereby the stem is able to move freely in the body in its longitudinaldirection.

A gap between the stem 4 and an inner wall 6 of the body 2 forms theactual air flow channel. The outer diameter D4 of the stem is typicallybetween 0.5 mm-1.4 mm and advantageously between 0.6 mm-1.2 mm in thecase of passenger car tyres and between 0.7 mm-2 mm and advantageouslybetween 0.9 mm-1.6 mm in the case of lorry tyres.

A diameter D5 of the valve disc is larger than the inner diameter D2 ofthe body and e.g. between 1.5 mm-4 mm and advantageously between 1.8mm-3 mm in the case of passenger car tyres and between 3 mm-8 mm andadvantageously between 3.2 mm-6 mm in the case of lorry tyres.

A front surface 7 of the valve disc, which is directed towards theinside of the vulcanising mould and comes into contact with the outersurface of the tyre blank in a way described below, is usually planar orcan have been shaped concave or convex either irrespective of apredetermined surface shape of the tyre or in accordance with apredetermined surface shape of the tyre.

A support surface 8 of the valve disc, which valve disc in the closingposition of the air venting valve (FIG. 4) supports itself on a stopsurface 9 of the body 2, can typically be of the shape of a truncatedcone. The shapes of the support surface 8 of the valve disc and the stopsurface 9 of the body on the side of the vulcanising mould are thuscongruent such that they set tightly against each other in the closingposition of the air venting valve. The stop surface 8 being of the shapeof a truncated cone, it forms a recess 10 on the inner surface of themould, in which the valve disc in said closing position sets so that thefront surface of the valve disc comes substantially on the same level oron the same height with the inner surface of the mould at that point.The diameter of the recess is substantially equal to the diameter of thevalve disc.

In the air venting valve, a coil spring 12 is pressed between an inneredge 11 at the lower end of the body 2 and the valve disc 5, whichspring keeps the moving inner part 3 formed by the described stem 4 andthe valve disc 5 extended in the direction of the inside of thevulcanising mould, whereby the air venting valve can be in its openposition in which the valve disc is a clearance away from the stopsurface.

In the valve according to the invention, there is e.g. a 0.2-0.8 mmfunctional aperture (clearance). Furthermore, the inner part 3 issubstantially longer than the body and, further in the arrangementaccording to the invention, there is an outer thread 13 in the lowerpart of the valve stem. A respective inner thread 14 is in the lowerpart of the valve body (the lower part of the channel), between the edge11 and a lower edge 15. Thus, it is possible to provide locking byscrewing the valve stem past the thread of the body, i.e., in theinstallation stage, the valve disc is screwed through the body, wherebyit stays permanently fast.

For facilitating installation, an end 16 of the inner part is downwardsconvergent, e.g., in the shape of a cone.

The air venting valve 1 according to the invention operates in thefollowing way for removing air from the vulcanising mould of the vehicletyre during the vulcanisation of the tyre:

A tyre blank is set in the vulcanising mould, which blank is caused toexpand by pressing air and/or steam inside of it, whereby the outersurface of the tyre blank presses against the mould surface gaining itsfinal surface shape, i.e. the surface pattern of the tyre tread, fromit. At the same time, the vulcanising mould is heated for vulcanisingthe rubber material of the tyre blank and for achieving the finishedtyre. In order for the outer surface of the tyre blank to set asprecisely as possible against the inner surface of the mould, air isremoved from between the tyre blank and the mould surface via airventing valves, air venting channels and their possible extensions.

For installing the air venting valve, in the arrangement according tothe invention, the valve body is detachable and the valve can beinstalled from the front i.e. from the opposite side of the mould eitherby pressing or by rotating, whereby there can be projections in thevalve in its body for turning it closed/open.

In the lower part of the valve stem, there is a thread as describedabove. There is a respective thread in the lower part of the valve body(the lower part of the channel). Locking is provided by screwing thevalve stem past the thread of the body i.e., in the installation stage,the valve disc is screwed through the body, whereby it stays permanentlyfast. When the thread in the valve stem ends, it stays fast because thethread part is larger than the free hole when they are not within eachother.

For installing the inner part of the valve, either a spanner, a magnetor a combination tool of them is used. When using the spanner, there isa shaping at the upper end of the valve for using the spanner.

For removing is required either pressing the valve from behind the mouldand rotating or a magnet for lifting the valve for 0.4 mm andsimultaneously for rotating the valve stem in the open direction. Forremoving is used a special tool which is either a spanner or a magnet ortheir combination. With the magnet, the valve can be lifted against aspringback factor whereby the thread in the stem can be set in place forscrewing it off.

FIGS. 4 and 5 further show a valve according to the invention whenclosed (by an external force, FIG. 4) and when open (by a springbackfactor, FIG. 5).

FIG. 6 shows the engaging relationship between the valve stem and thevalve body; FIG. 7 shows the valve stem and FIG. 8 shows the valve body.

It is well known by those skilled in the art that the differentembodiments of the invention are not solely limited to the exampledescribed above, but they may vary within the scope of the appendedclaims. The invention can also be applied to others than the vulcanisingmoulds of a vehicle tyre, whereby, by using an outer thread or an outerthread in which is installed a stopper to prevent the valve fromrotating too deeply, the tolerance demand of the boring can bediminished and the breaking in the installation stage or respectivelythe detachment of the valve due to too large a hole can be prevented.

1. A method for removing air from a vulcanising mould of a vehicle tyreduring the vulcanisation of the tyre, whereby a tyre blank located inthe vulcanising mould is caused to expand and to press against a mouldsurface, in which method, air from between the tyre blank and the mouldsurface is removed by air venting valves (1), in which there are a body(2) and in it an inner part (3), comprising a moving stem (4) and avalve disc (5) respectively moving in the area of the mould surface,which valve disc closes this air venting channel when the tyre is in itsfinal form against the mould surface, characterised in that, in themethod, the body is substantially cylindrical of its outer surface andis arranged detachably in the mould, and in the lower part of the innerpart is arranged an outer thread and in the lower part of the body arespective inner thread so that the inner part of the valve isinstallable by screwing the valve stem in the body.
 2. A methodaccording to claim 1, characterised in that the vulcanising mould is avulcanising mould of a vehicle tyre, and the inner part (3) issubstantially longer than the body (2), and in the lower part of theinner part is arranged an outer thread and in the lower part of the bodya respective inner thread so that the valve is installable by screwingthe valve stem past the body thread i.e., in the installation stage, thevalve disc is screwable through the body.
 3. A method according to claim1, characterised in that for installing the inner part of the valve isused either a spanner, a magnet or a combination tool of them.
 4. Amethod according to claim 1, characterised in that when using thespanner there is a shaping at the upper end of the valve for using thespanner.
 5. A method according to claim 1, characterised in that forremoving is required either pressing the valve from behind the mould androtating or a magnet for lifting the valve and simultaneously forrotating the valve stem in the open direction.
 6. A method according toclaim 1, characterised in that in removing is used a special tool whichis either a spanner or a magnet or their combination.
 7. A methodaccording to claim 1, characterised in that for removing with the magnetthe valve can be lifted against a springback factor whereby the threadin the stem is re-set for screwing it off.
 8. A method according toclaim 1, characterised in that the valve body is installed,advantageously from the front, by rotating, whereby there can beprojections in the valve in its body for turning it closed/open.